The conventional sleeping bags may be classified into two types, i.e., the feather sleeping bag and the cotton sleeping bag; in fact, the aforesaid two types of sleeping bags have the same structure except as for the internal filling elements. The conventional sleeping bag usually comprises two layers, i.e., one inner lining and one outer case sewed together; and the edge thereof is usually equipped with a zipper. After the sleeping bag is folded up and edges thereof are joined together, the sleeping bag is formed. When a sleeping bag is unfolded, it looks like a flat pad; however, the conventional sleeping bag has some drawbacks, as follows:
(1) Between the inner lining and the outer case, a given quantity of cotton or feather is filled; then, the two layers are sewed together. Whenever the weather changes, the sleeping bag may either fail to keep the human body warm or provide too much warmth to the user; as a result, the user would hardly get to sleep.
(2) During camping, the sleeping bag, a blanket is usually added anticipating the rapidly changing weather condition; however, the sleeping bag usually is not provided with any means to hold the blanket in the desired place; the blanket is thus susceptible to move away when user turns or moves, and the user would then often have an uncomfortable sleep.
(3) Before sleeping when camping out, the ground surface is first covered with a moisture-proof cloth or a piece of soft pad to pervent water or moisture infiltration, or to alleviate a rough or uneven ground surface. When the sleeping bag is placed separately on a moisture-proof cloth or a soft pad, the sleeping bag is still susceptible to separating from the moisture-proof cloth or the soft pad whenever the person in sleeping bag makes a slight move or turn; the cold air or moisture would then infiltrate into the sleeping bag affecting the person's sleep or health.
(4) When used for a considerably long period of time, the sleeping bag would get an odor from sweat and be contaminated by dirt; therefore the sleeping bag must be cleaned or washed. As the cotton or feathers have been fixedly filled in the sleeping bag, it is quite inconvenient for the user to take out the cotton or feathers before washing the bag.